Submitted to: Eastern Oregon Agricultural Research Center
Publication Type: Experiment Station
Publication Acceptance Date: 2/1/2004
Publication Date: 6/12/2004
Citation: Boyd, C.S., Svejcar, A.J. 2004. Production and regrowth of riparian sedge/grass communities. Eastern Oregon Agricultural Research Center. Range Field Day Report 2004: Current Forage and Livestock Production Research. Special Report 1052. p. 32-39. Interpretive Summary: Riparian areas are considered relatively sensitive to livestock grazing, largely because livestock are attracted to these plant communities once the uplands become dry and less palatable. The height of grazed vegetation (stubble height) is often used as a tool to determine when livestock should be moved from one pasture to another. There have been few studies to help managers gauge the potential for regrowth between early to mid summer and fall. Many recommendations are based on fall stubble height. We demonstrated that if two to four inches of stubble remain after early summer grazing, there is substantial regrowth by October.
Technical Abstract: Stubble height regulations are frequently used to manage livestock grazing of herbaceous riparian vegetation. The objective of this study was to determine the impact of clipped stubble height and time of clipping on production and regrowth of herbaceous riparian vegetation. In June and July of 2000-2003, 2.2-ft2 experimental plots were clipped to stubble heights of 2, 4, or 6 inches, and paired control plots were left unclipped. All plots were clipped to ground level in October and regrowth was calculated by comparing clipped and control plots. Results indicate that 1) height of regrowth was associated positively with stubble height and 2) regrowth was less with July compared to June clipping. Annual production was higher with July (3,430 lbs/acre) compared to June (3,169 lbs/acre) clipping but did not vary be clipping height. Production values for clipped plots were higher than for unclipped plots, indicating compensatory production in response to defoliation. Timing and intensity of defoliation were reliable predictors of regrowth and production performance. Most clipping heights by time combinations produced end-of-season heights sufficient to meet current federal stubble height requirements (i.e., 4-6 inches). Our results provide insight on the timing and intensity of defoliation that will allow for adequate regrowth to meet different management objectives. However, other factors such as stream channel morphology, animal selectivity, and annual weather variation will need to be considered.